I'll try to help...not impress.
As I said I have a 225 watt pelt chiller.
same mobo, xp2600@ 2600mhz (12.5 x 208) water cooled cpu, water cooled nb
I can maintain 22 (c) regardless of load in a 26~28 ambient room. The cdr, hdd will add little to that load...the radeon will add and I think (from several friend experiances) you should expect the water temp to rise 1.5~2 degrees (c). Your stumbling block is the radiator inside the case. The pelt is actively cooling water...a radiator is going to try to equalize temps and problably be more efficiant at it that than what ever watt pelts you can throw into the mix. Dump the radiator concept and you should see water temps of around 24 (c) with ambient @ 26~28. If that isn't cool enough add some more pelts. This is assuming you are water cooling the pelts (dual loop) with ambient temp water.
wj
my water cooling